Pond Collection

By far the most abundant and diverse herbivores in terrestrial ecosystems are insects, which have the mechanisms described below are many more, including detoxifying most of the wide range of chemicals that plants produce to deter herbivory. Since the extinction of the dinosaurs, many of which ate plants, at the end of the Cretaceous, mammals evolved to become the largest and most diverse vertebrate herbivores on land; many birds also eat flower parts, fruit and seeds, but only a few reptiles and fish eat plants.

Herbivorous mammals, like insects, have evolved the capacity to detoxify plants’ chemical defences and to overcome their mechanical protection. Mammalian teeth bite, gnaw and chew nuts, seeds, roots, silicious grass stems, bark and wood in many different ways.

Chewing, homeothermy and symbiotic microbes that aid digestion enable mammals to extract maximum nourishment from tough, nutritionally poor diets. Plant tissues contain less sodium and calcium than vertebrate bodies, so all herbivorous mammals need supplementary minerals, especially growing juveniles, breeding females and adults that replace their antlers annually. Specialists on non-photosynthetic, tissues such as seeds and roots, also need sources of iron. So most vertebrate herbivores, especially large species, chew animal bones in carrion (the edges of the Minke whale scapula displayed in the Foyer have been nibbled, probably by sheep, deer and rodents), lick blood (containing iron and sodium) from wounded animals, visit cliffs and caves where fragments of mineral-rich rocks are found, and mothers usually eat their placenta after giving birth. Elephants use their trunks to suck up mud containing such nutrients.

Herbivorous birds and reptiles eat fragments of eggshell, molluscan shells & cuttlebone and carrion, especially while breeding. Parrots use their strong hooked beaks (see Box C3 and D4) to prise soft mineral-rich rocks off riverbanks and cliffs, and even nibble mortar in old walls.

Large quantities of bulky plant material are needed to sustain herbivores, so their stomachs are usually large and their guts longer than those of carnivores of similar size. Studies on domesticated cattle (see Box C1) show that mechanisms of uptake of these nutrients, and vitamins synthesised by their symbiotic bacteria from the digesta in the gut. Other very efficient mechanisms direct essential fatty acids into cell membranes of the nervous and immune system (and away from being wasted as fuel). Many herbivores are thus able to grow remarkably fast on what would be a very meagre diet for humans. Thermogenesis in brown adipose tissue may be important in ‘burning off’ excess carbohydrates in rodents and other mammals with ‘unbalanced’ diets: to obtain enough proteins and minerals, they overeat starchy seeds. Proteins and fats are also scarce in plant diets so many groups, e.g. pigs, rats and many monkeys, also eat some animal food.

Eating plants is slow, so herbivores spend much time exposed to weather & sunshine, and predation, which they avoid with shells, camouflage, being toxic or distasteful, or just being alert and quick to run, fly or swim safety.

Perissodactyls graze and browse foliage with their strong flexible lips and incisor teeth, chew their tough diet with side to side movement of the lower jaw, then digest it with the aid of microbes in the colon. In the horse family (Equidae), the dentine, enamel and cementum layers of the long molar teeth are folded into ridges forming a grinding surface suitable for chewing tough, abrasive grasses. These teeth erupt very slowly throughout life: this small horse had a good diet, so the rate of wear of the molar teeth matched their rate of eruption, forming straight rows of healthy functional teeth. But the dentition of the elderly donkey became grossly deformed, with some molars overgrown and others worn to the roots, until eventually it could not chew. It was close to starvation, with its skull and other bones much weakened by depletion of their mineral and collagen (broken down to generate energy) before it was destroyed, see small hole in the cranium.

The structure of the legs of horses (and zebras, asses etc) is explained in Box B4. They can move fast and efficiently over hard, uneven ground and to jump over small obstacles; the hind legs can deliver a powerful kick.

In tapirs and rhinoceroses, digits 2,3 & 4 form three toes, each with its nail surrounding a firm but flexible pad. They can move silently through dense vegetation and gallop short distances when required. As in horses, rhinoceros lips pluck the vegetation and their molar teeth grow continuously as they wear through vigorous chewing; the separate teeth are from older black rhinos in which the tooth roots have closed and the crowns are very worn. The emerging back molar teeth seen in the skull and jaws of this white rhinoceros show that it was a young animal.

Perissodactyls were abundant and diverse in the Eocene, 40 Mya, declined slowly as artiodactyls diversified, and have fared badly as humans became more numerous and widespread. All five extant species of both tapirs and rhinoceroses are endangered, with one reduced to two living specimens (see Northern White Rhino skull in the Foyer). As described in Boxes A1 and C1, domestication has saved horses and asses from a similar fate. Zebras are now the most abundant wild equids, but one species, the quagga, was hunted to extinction in C19th.

Artiodactyls are now by far the most abundant and diverse large mammalian herbivores. The pig family (Suidae), such as this peccary from Central America, roam forests in family groups eating roots, nuts, seeds plus small prey and carrion. They dig with their snouts as well as with their feet that have a pair of large central toes with a smaller digit on either side. Their dentition and digestion are less specialized to a diet of tough foliage than those of the ruminant artiodactyls. In many suids, especially the males, the canine teeth grow throughout life, protruding from the mouth to form impressive tusks, as in this warthog. Like horns and antlers, tusks serve in both formidable defence against predators and assertion of male dominance.

Camelidae (camels, guanacos, vicuña etc.) eat grasses and foliage which they tear between their lower incisor and upper lip and chew with side to side movement of the lower jaw and large stout molars, as seen in this two-humped camel. They have multi-chambered stomachs and chew the cud and, especially in desert species, the digestion, metabolism, excretory and immune systems have many unique features that enable such big animals to thrive on irregular supplies of very poor quality food, go without drinking water for unusually long periods and tolerate large fluctuations in body temperature. Camelid feet are reduced to two toes and they have flexible pads instead of hard hooves; they do not have horns but their long sharp canines are effective defence. The hump(s) contain storage white adipose tissue but in other respects the distribution of fat stores is similar to that of other artiodactyls. Most extant camelids live at high altitude or in deserts and have fine woolly hair that protects them from cold and heat, see Oak lower Shelf.

Bovids (bison, buffalo, cattle, sheep, antelopes) and cervids (deer) have cloven hooves, making them more agile especially on very steep, or slippery terrain. They are ruminants with four-chambered stomachs that graze and browse foliage with strong flexible lips and lower jaw incisors, missing in this yellow-backed duiker, a small antelope, biting on toothless horny pad covering the tip of the upper jaw. They chew with side to side movement of the lower jaw that enable the long rows of molar teeth to grind foliage. All bovids in the British Isles are domesticated or feral, and Europe has only a few relict populations of truly wild bovids (see Boxes A1 & C1).

In contrast, Britain’s two indigenous cervids, roe and red deer, are still widespread and in places abundant, as are fallow deer, introduced from France in C11th, and three smaller species introduced from Southeast Asia around 1900, including Chinese water deer (see Oak, top Shelf) and muntjac, a solitary forest deer. This young adult muntjac’s molar teeth are in good condition so it could chew foliage thoroughly. But the molar teeth of this roe deer, which was found dead in an Oxford garden, are worn so smooth that it could not chew and had died from starvation. In natural ecosystems, predators would have killed such elderly animals as soon as they became too weak to run fast.

The smallest species of both families are about the size of a domestic cat as adults but many bovids, and a few cervids, are very large as adult, as indicated by this cervical vertebra, probably from an eland. In life, the nerve cord ran through the large central hole, the blood vessels to the brain though the two lateral holes. Many species live in herds dominated, at least during the mating season, by one mature male. In all but the most primitive deer and reindeer (see Oak 2nd Shelf), mature males grow antlers, consisting of keratin overlying a bony core, as seen in these roe deer aged 1 y (front) & 2 y (behind). After each mating season, the antlers fall off, leaving the stags resembling the hinds. They start to regrow several months before the next rutting season, becoming larger and more elaborately branched every year (see Box A1), so the number of tines indicates a stag’s age. This sub-fossil antler base, possibly an Irish Elk, shows the solid outer bone enclosing more spongy inner bone, and the ‘abscission zone’ where bone cells died, weakening the bond between the skull bone and the antler.

All adult male bovids, and in some species, adult females, have horns that are also hard keratin overlying bone but with a few exceptions, are unbranched, for example this yellow-backed duiker, a solitary forest antelope of west Africa. Bovid horns (see also Boxes A1 and A3) grow continuous from puberty into forms and sizes that differ greatly between species of apparently similar habits and habitats. The skull bones from which antlers and horns grow usually thicken and form more elaborate sutures (see ram skull in Box A4), protecting the brain and eyes from injury.

Unique properties of the teeth enable elephants (and mammoths) to grow to 6.5 tons and live up to 70 y on a diet of tough, abrasive grasses, nuts and wood. Elephants cannot bite; the trunk, a muscular extension of the nose and upper lip, gathers vegetation and places it the mouth, aided by tusks that dig for roots and pull branches from trees.

They have the same number of molar (chewing) teeth as other mammals but the molar teeth of each jaw are used sequentially, not simultaneously as usually happens. These teeth are from African bush elephants, with the gumlines marked in red. As the broken tooth shows, each tooth has several roots and pulp cavities that contain the cells that form the pale yellow dentine; this hard, calcified layer grows from the inside so it thicker near the tip than at the root. The enamel and cementum are added from the outside, and together form ridges that enable opposing teeth to grind vegetation.

The next four teeth illustrate tooth replacement; only the portion of the tooth above the gum would be visible in the mouth. The smallest is from a calf around weaning: as its ridged surface grinds grass, the tooth wears down to the gum line, but the surface is smoother and the gumline higher at the front of the tooth. As its surface wears smooth through use, the tooth slowly moves forward in the jaw, and its roots close, so the dentine forming cells, blood vessels, nerves etc die, as seen in the next size tooth. Its crown has worn thin and its roots are disintegrating, so it is about to fall out. By then another, larger tooth has formed behind it and moves forward to become the main chewing surface until it is worn smooth, dies and falls out, as shown in the lower jaw of this half-grown elephant.

This process continues throughout life: the molar teeth in both upper and lower jaws move forward as they wear and die to be replaced with larger teeth that form at the back of the jaw as they (and the rest of the skeleton) grow. Molars of mature adults weigh up to 5 kg each and in massive jaws, they and the tusks make elephant heads very heavy, but use of the muscular trunk for drinking and gathering food enables the neck to be short and very firmly attached to the spine. The largest molars may last a decade, but when its last teeth are worn out, the elephant cannot chew and eventually dies of starvation. If the rate at which the food abrades the teeth fails to match the rate of tooth replacement, the dentition can become as distorted and dysfunctional, as that of the donkey in Box A3.

In the elephant family, the second incisor teeth in the upper jaw form tusks grow throughout life, becoming massive in mature males. As this small tusk from an Asian elephant shows, they have the same basic structure as other mammalian teeth with a central pulp cavity. In most mammals, teeth function inside the moist mouth and the dentinal tubules are more or less parallel (so young teeth split when dried, as in the tiger in Box D2). But in protruding tusks, the dentinal tubules are arranged as two opposite helices, forming the cross-hatched pattern of fine lines, seen in this pendant and in the billiard ball, in which the pulp cavity is reduced to pin-hole size, showing that it was carved from near the tip of the tusk of a fairly old elephant. This structure makes the tooth mechanically isotropic, resistant to twisting and bending when digging, tearing bark and branches from trees or fighting, and it does not crack or split as its dries. Similar properties have also evolved in slightly different ways in walrus and narwhal tusks (see Box C2) warthog tusks (see Box B3) and hippopotamus teeth.

Elephants can walk very quietly on their 4 or 5-toed feet. The position of the toenails shows you the position of the digits in the skin of this right hind lower leg of an Asian elephant, and dried sole of a fore foot from an African elephant. Large pads of fibrous adipose tissue (see Box A4) form a cushion between the bones and the soles which are hard-wearing but flexible. Sense organs in the feet enable elephants to ‘hear’ low frequency vibrations passing through the ground, which could be important in maintaining contacts between family groups. Elephants may be able to hear distant thunderstorms that generate the pools and fresh grazing that they need. Their olfactory sense is also excellent, rendered directional by raising and turning the trunk.

Elephants are born into small herds of related females and their calves. They communicate with each other using a range of rumbles, squeaks and loud roars, the latter also deployed to deter predators, and probably also by pheromones. Males are expelled from the natal herd when nearly mature, and become solitary except during the mating season. Females usually remain with their families, forming strong bonds that persist after death: many observers report that the herd visits the site of a recent death, sniffing and lifting relics such as bones and skin. Elephants have long memories, recognising each other after prolonged separation, and remembering routes to resources such as water and mineral deposits.

Like other mammalian herbivores, symbiotic microbes, mostly in the caecum and colon of the hind gut, aid digestion of tough vegetation. Microbial metabolism releases much heat so, although newborn elephants have sparse hair over the head and body, after weaning thermal insulation is not necessary, though a few scattered hairs can be seen in this fragment of thicker skin. Elephants dissipate excess heat by flapping their huge ear pinnae, where the skin is much thinner.

The most numerous, widespread and diverse mammalian herbivores are rodents; they gnaw tough vegetation with their continuously growing, curved incisor teeth, often hardened with red iron salts in the outer enamel as seen in the coypu and beaver. The paca (found in Central & South America) gnaws nuts, seeds, roots and stems as well as nibbling fruit and leaves; in this lower jaw, the left incisor is in situ but the right has been pulled out from its roots at the back of the jaw to show the long tooth that grows continuously as its tip is worn away. These front teeth are quite different from the grinding molars, as seen in this lower jaw of a coypu, which also shows the wide flanges that support big, strong jaw muscles.

Rodents can slide the lower jaw forwards to engage the incisors for gnawing, as in the left squirrel skull, or backwards to chew with its molars as seen in the skull on the right. This mechanism enables beavers to fell trees like this silver birch, grooved by sharp incisor teeth, as well as to chew leaves, bark and wood. Certain rodents including beavers, squirrels and rats manipulate food in their front paws, as primates do. They also build nests and/or food stores, and in the case of beavers, damns and lodges, using a variety of calls to communicate with each other.

Intensive study of laboratory rats and mice reveals that they (and probably most rodents) have very efficient digestion and metabolism and thus fewer specific dietary requirements, making them far superior to humans in these respects. Some rodents, especially small species, eat earthworms, large insects and fungi as well as nuts and grain, and many more obtain nutrients such as essential amino acids and sodium, calcium and iron from eating animal carrion (as well as nuts and seeds), especially while breeding.

The house mouse has raided human food stores for around 15 Kya, nibbling into dried grains and nuts with the sharp little teeth and stout jaws, shown in this beautifully prepared specimen. This species has adapted its diet and habits to that of its human providers; cheese, containing the calcium salts, proteins and essential fats of milk, plus added sodium chloride, is irresistible. House mice originated in India and with human help, have spread all over the world, entering Europe only about 3 Kya. Living in close proximity to people for their warm homes as well as their food stores and meal scraps, mice acquired many human genes long before they were co-opted into research.

Rats are also omnivores, raiding birds’ nests for eggs and chicks, as well as eating carrion, grain and human scraps. Travelling on ships, then ‘landing’ by climbing along ropes at night has enabled them to colonise thousands of islands that they would not have reached without human help.

Many small rodents in temperate and arctic regions hibernate during the winter e.g. marmots, dormice and chipmunks. Their core body temperature falls to around 5 oC and since they do not forage, digest, grow or breed, their rate of energy expenditure is very low. Hibernation sites must be dry, protected from freezing and most important of all, at near-constant temperature: if they wake up during premature warm spells, they consume their energy reserves much faster and may be unable to find enough food to avoid starvation. They rewarm by activating brown adipose tissue, a thermogenic tissue unique to mammals that is also important in enabling neonates to maintain normal body temperature.

Voles, field mice, ground squirrels, guineapigs, lemmings and hamsters breed prolifically and are often abundant in their natural habitat. Their grazing and gnawing, and their habit of burying nuts and seeds intended for future consumption but often never reclaimed, significantly modifies the local flora. They are important food for predators such as owls, falcons, hawks, foxes, stoats, pine martens and snakes.

The teeth of lagomorphs, rabbits, hares and pikas, are similar in form to those of rodents, but they are more strictly vegetarian, and their molars as well as incisors grow throughout life. Although most are small and live at high latitudes and/or high altitudes, they do not hibernate.

Hyraxes are also herbivores, most closely related to elephants (see Box C3) and manatees, with peculiar combinations of anatomical and physiological characters, including slicing their plant food with their molar teeth as cats do with meat. The few living species inhabit dry, rocky areas in Africa and Arabia, but fossils show that they were much larger and more diverse in the past.

Most primates, especially large species such as apes and this pig-tailed macaque monkey, are mainly herbivorous, eating flowers, fruit, new leaves and other soft plant tissues, plus small prey, eggs and carrion. Most live in large social groups, helping each other find food, and avoid predators. They often grasp and tear food with their hands. Macaques weigh around 15 kg as adults, about 20% of human body mass, but their incisor and molar teeth are about the same size. Our ancestors cut, crushed, later cooked and ground, components of a diet similar to that of other higher primates; their greater manual dexterity allowed the evolution of proportionately smaller, weaker teeth on shorter jaws.

Herbivory has also evolved in metatherians, especially Australian groups, such as this young wallaby. Its molar teeth resemble those of similar sized bovids and cervids (see Box B2) but the front of the jaws is very different, with upper incisors biting against recumbent lower incisors.

Herbivorous birds specialise on certain plant parts, but most also eat some animal food, worms, large insects and carrion, especially while laying eggs. Swans, geese and ducks plus ostriches and rheas eat green vegetation collected in their long horny beak with sharp serrated edges. Toucans, hornbills (see Box B1) and many others specialize on fruits and berries, but several bird families prefer the concentrated nutrients in seeds, including finches and some other passerines, parrots and phasianids: pheasants, partridges, grouse, peafowl, turkeys, quail and junglefowl. Large parrots can crack hard nuts in the beak with jointed upper jaw, while holding them firmly with one foot (see Box C4). Doing so takes skill, and most such parrots always use the same ‘dominant’ foot, usually the left; footedness, like human handedness, makes complex tasks quicker and more efficient.

A few lizards, such as this iguana eat foliage, at least when large, basking in sunshine to aid digestion of their food, but since the dinosaurs disappeared, tortoises became, and still are, the most abundant and diverse reptilian herbivores. The strong beak is covered in hard, continuously growing keratin, sometimes forming a serrated edge and they too aid digestion by basking in sunshine. Note the horny biting surface of the lower jaw and the scaly leg and curved humerus, which can, with the head, be pulled into the shell for safety.

Teleost fish can swim backwards (in contrast to most other groups) and hover, enabling this parrotfish to nibble algae and encrusting invertebrates.

Many gastropod molluscs use their radulae to rasp leaves and other soft vegetation on land, such as this edible Roman snail, or in freshwater, and this abalone which grazes on marine algae.

Insects, especially caterpillars, grubs and other larval stages, are the main consumers of terrestrial plants, roots, bark, wood and seeds as well as leaves and flower pollen & nectar. They range from generalists like locusts which eat many different species of plant, to certain caterpillars that can feed only on one or a few similar species, having specific biochemical mechanicals that detoxify the antiherbivore chemicals therein. The millions of herbivorous insects are represented by this male Hercules beetle which eats fruit and tree sap, but he grew as a larva on a diet of rotting wood.

Humans, and their ancestors going back at least 6 Mya, are omnivores, eating foliage, roots, seeds, carrion and small prey. Increasing brain size required more nutrients and energy, so the proportion of nuts and vertebrate tissues in the diet increased.

Various invertebrates, such as these oysters, were collected from beaches and shallow seas; they could be opened with very simple tools –some coastal monkeys do the same. Fish, European river perch, were eaten wherever they could be easily caught. Around the Polynesian islands and coasts of Asia and Australia, sea turtles and their eggs yielded much delicious food.

Catching and butchering large terrestrial mammals needed more tools and better organisation, but were highly nutritious. Subfossil bones and cave paintings show that in Africa and Asia groups of people hunted various large birds, reptiles and mammals, especially bovids such as this Thomson’s Gazelle from East African Savannah. Note that this male’s horn is still growing at its base, and the upper ridges show clear signs of wear. In Europe, people ate wild horses, mammoth, bison and deer (see Boxes A4 & A,B & C3), though by historic times, only the deer were still widespread and common in the wild. North America provided caribou (=reindeer) and buffalo and large rodents (see Box D3) and small camelids like the guanaco were hunted in South America.

Species of the pig family were widely hunted because they are a convenient size and run quite slowly, but are not defenceless: wild boar of Europe and central & southern Asia have formidable tusks, like those of African warthogs (see Box B3), and can fight fiercely. Wild boar in Britain were hunted to extinction around 1400 for their meat and bristles (see Oak, lower Shelves) and disappeared from agricultural areas of mainland Europe such as Denmark by 1800 but remained common in forests. In some European cities, wild boar have recently become a nuisance, boldly foraging on human garbage as foxes do. And in southern Britain escapees from farms and menageries have re-established wild populations.

By the Late Pleistocene around 100 Kya, Homo sapiens had expanded into Eurasia, where the climate was fluctuating and often very cold, and interbred with archaic species of Homo, leading to their disappearance. H. sapiens were itinerant hunter-gatherers who used animal skins as bedding and clothing (see Oak, lower Shelves) and made equipment from stone, wood, various plant fibres and animal tissues. So they were collecting more materials, interacting with more species and eating a wider range of foods.

Living bone is strong but it tends to warp and crack when dry, especially if it was still growing and thus consisted of more protein but less mineral than mature bone (see young tiger Box B2 and bottlenosed dolphin in Box C2).

As explained in Boxes C2 & C3, certain teeth form protruding tusks that do not split when dry, rot when damp even more slowly than most other vertebrate teeth and, especially those of the elephant family, are mechanically isotropic, so are ideal for carving. People have collected all these materials for making needles, fishhooks, body ornaments and other strong, durable objects for which we would use hardened steel. Humans in Europe have carved mammoth tusks for at least the past 42,000 y, and elsewhere those of elephants probably for longer. Before plastics were invented a century ago, ivory from subfossil mammoths as well as from elephants, was a valuable, widely traded commodity for making beads, billiard balls, piano keys and ornamental and ritual objects.

Bovid horn and cervid antler share many of the properties of ivory, and though not as strong, are more plentiful. Antlers also grow into shapes convenient for use as picks, and until very recently were made into handles on knives and walking sticks.

Rhinoceros horn, which is congealed stiff hairs, has long been valued as a light-weight, easily carved material for making handles of daggers, cups and ornaments. It is also used medicinally though there is no evidence that it is effective. People used many other animal parts to make tools (e.g. walrus tusks Box B3), musical instruments and adornments: this necklace contains rodent incisor teeth, probably from muskrats, a large semi-aquatic rodent native to Canada and northern USA. The canine tooth is from an adult felid, probably a leopard, note that the root is longer than the crown.

The coarse bristly hair of suids and some large rodents, such as African porcupine quills had many non-food uses, including as brushes, needles and as here making light-weight containers. Other uses of animal fur and skins are described in Oak, lower Shelves.

When parchment (see Oak lower Shelves) and later paper replaced papyrus as a writing surface in the early Middle Ages, the primary flight feathers of large birds (see Box C4) were used as pens. When in situ, quills, such as these from a Canada goose, are tough flexible tubes containing blood vessels which nourish the epithelia that secrete keratin. The core tissues dry when the feather is shed (or pulled out) so are easily extracted, leaving a protein surface that readily holds ink. The walls can be stiffened by heating, making the quill easy to cut with a ‘pen-knife’. Large geese and swans produced the highest quality quills that could be trimmed to form tips suitable for writing sacred texts, legal & diplomatic records etc., but adult birds yielded only about a dozen such pens/year. The need for quills prompted legal protection and active management of wild mute swans in western Europe, among the earliest legislation that combined sustainable harvest with successful conservation. Less important documents, such as business accounts and registers in rural churches, were often written with quills made of secondary flight feathers or from those of smaller birds. Steel nibs on dip pens were invented two centuries ago, replaced by fountain pens in the 1950s, and later ball points.

Another major use of feathers was in bedding, clothing and millinery. Down was collected from birds’ nests, especially eider ducks that breed near northern European coasts, for making ‘eiderdowns’. The Plumage League was started in the 1880s by a group of women opposed to the slaughter of wild birds, egrets, pheasants, grebes and exotic ostriches & birds of paradise, to adorn ladies’ hats with their attractive feathers. The League eventually became the Royal Society for the Protection of Birds.

Hornbills are medium-sized birds of savannahs and rainforests in the Old World tropics, with broad wings, long tails and disproportionately long colourful beaks topped with a casque, largest in adult males, that may amplify their calls and act as a weapon in fights. In most species, the interiors are spongy, but the casques of helmeted hornbills of Southeast Asian forests are solid keratin, gold-coloured with a scarlet surface formed by oxidation of the preen gland secretions that the bird spreads over it. This ‘hornbill ivory’ is softer and much less dense than mammalian ivory, and has long been carved into elaborate decorations in Malaysia, Borneo and southern China. The species is now critically endangered.

In a single species, the hawksbill sea turtle, the outer keratinous layer of the shell is unusually thick, forming ‘tortoise shell’. Until plastics were invented, this light, flexible, non-allergenic material was used to make spectacle frames, hair supports, furniture inlays and decorative objects such as this cigarette case, that also has inlaid mother of pearl. Plastic imitations of the tortoise shell pattern are still popular for spectacles and hair clips. This relatively small marine turtle (compared with that in Box A1) feeds on sponges and reef corals in tropical and subtropical coastal waters and lagoons, where it easily caught; previously widespread, it is now critically endangered, though conservation projects in Australia and the Caribbean protect breeding sites.

Many animals have long been used in rituals and ceremonies, which was probably why the skin of this varanid lizard was mounted on a stick.

Many invertebrate skeletons, like those of vertebrates, are combinations of proteins and minerals, usually carbonates or silicates. The inner surface of the shells of most bivalves and some gastropods is composed of nacre, layers of secreted chitin and silk-like proteins impregnated with very tiny aragonite crystals. Being in contact only with the soft body, nacre is not exposed to wear and damage. In this abalone shell (a gastropod, see also Box D3), the nacreous layers are thin enough to produce iridescence, differential refraction of light that produces lustrous colours called mother of pearl; the material was for centuries, and is still, used to adorn luxury items (see ‘tortoise shell’) and to make buttons for women’s clothing.

Pearls are of similar composition and form naturally when foreign objects such as a tiny sand grain get under the nacre-forming layers of the shell, as shown in this mussel shell (‘cultured’ pearls are created by artificially inserting such ‘seeds’). They are hard enough to be drilled and polished for use as jewellery. Pearls enlarge slowly as more layers of nacre are added, so the biggest and most lustrous pearls are found in the shells of the oldest molluscs, hence their rarity.

Organic cameo ornaments and jewellery are carved from part of the shells of large gastropod molluscs, most frequently the bullmouth helmet shell. Its smooth, slightly curved underside, that in life is covered with fleshy mantle, consists of an outer cream or mottled layer that is easily carved, firmly attached to a reddish brown layer underneath.

The windowpane oyster (= Capiz shell) is a bivalve mollusc, note the V-shaped hinge visible on each ‘pane’, that is found in warm coastal waters around the Philippines and northern Australia. Unusually, the shell is mostly fibrous protein with only a little impregnated mineral, so it is translucent. It also takes up dyes, does not deteriorate when dry, is very low density, easily cut to shape and the trimmings can be boiled to make glue and varnish – and the flesh is edible. The oysters have long been used in buildings as a replacement for glass, but during C20th, huge numbers were harvested to make lampshades and chandeliers for export, abruptly depleting natural populations. Even in the tropics, oysters grow slowly so management policies are only gradually leading to recovery.

Most coral skeletons are calcium carbonate in the form of aragonite embedded in proteins secreted by the living tissues and are white, but some species living in iron-rich waters incorporate red iron salts, making them pink or red. When dry, such skeletons can be shaped into beads and other decorations.

Almost all of the 10,000 species of Phylum Porifera (sponges) are filter feeders, extracting fine particles of organic debris from the water. The majority have stiff, hard skeleton, composed of a little protein impregnated with much mineral, like this calcareous sponge, in which the tiny pores through which water passes are clearly visible. But the skeletons of a few closely related species are mostly fibrous protein containing very small silicious spicules, making them tough, elastic and water absorbent. The black living tissue has been cleaned off this bath sponge from shallow coastal areas of the eastern Mediterranean, leaving its gold-coloured dry skeleton. Their unique properties made them valuable for filtering water and wine, as padding and for personal hygiene, so since antiquity they have been traded all over Europe and western Asia; no wonder Linnaeus named the main species Spongia officinalis. For three millennia, bath sponges were collected by divers who could not work below 20-30 m, so the wild populations were maintained from breeding stock living in deeper water. But around 1900, the diving helmet and means of supplying air underwater were invented, enabling much more intensive harvesting, which was arrested only by the invention of cheaper but much less durable synthetic ‘sponges’ in the 1950s. Some natural sponges are now cultivated around fish farms where they extract particles of fish excreta and food debris, thus cleansing the water.

Domestication is selective breeding for particular traits, physical features such as body size and shape, reduction or absence of horns, capacity to thrive on certain diets, efficient prolific breeding under artificial conditions, and behaviours such as intelligence, alertness and cooperation with people (‘tameness’). The endocrine changes associated with the latter affect other characters, especially colour and texture of the skin and the hair, plumage or scales that it produces. The most noticeable and consistent is replacement of the natural skin pigmentation with mottled black/grey/brown/white, or pure white: horses and donkeys (i.e. piebald, skewbald or ‘grey’), cattle, sheep, goats, pigs, rabbits, guineapigs, dogs, cats, mink, geese, chickens, peafowl, goldfish and, within the past century, white laboratory mice and rats.

Of these traits, only body conformation is easily identified in animal relics. Domesticated animals often have shorter legs than their wild ancestors (thus cannot run as fast), but larger bodies and females are hornless. Such skeletal features have enabled archaeologists to conclude that sheep were among the first artiodactyls to be domesticated in western Asia around 8-10 Kya. Their wild ancestors were mouflon (see Oak 2nd Shelf), athletic, hardy, with huge, curved horns, found in the Caucasus region, Cyprus and mountainous areas of Europe. The cattle and sheep/goat families (but not antelopes) (see Box C2), and most other domesticated mammals naturally form nomadic herds that roam over a home range the mature males do not fight each other to defend a territory, although during the breeding season, they may fight for mating rights. Nonetheless, for millennia pastoralists have castrated male livestock soon after birth, selecting a few to sire the next generation as rams, billy goats, bulls (cattle & camel), boars and stallions.

These innate behaviours persist in domesticated sheep: for most of the year, shepherds can lead flocks composed of both sexes and all ages to graze over large areas. Some breeds, such as the tough, handsome, grey Herdwicks of Cumbria, have retained the ancestral ability, passed from mothers to offspring, to ‘heft’ to the area in which they were born and raised. Thus they can be left to roam safely over moors and other unfenced pasture. Horn is keratin that shrinks when heated; owners can mark adults with hot brands as convenient means of identifying their flocks.

Sheep were probably first kept for meat, milk, and skins until they were selectively bred to produce wool, which is underfur with few or no bristly guard hairs and usually white, though the ancestral brown or black frequently reappears even in modern breeds. Fine, crimped springy wool lends itself to spinning and weaving, and dyes work best on white. Most mammals native to temperate and arctic climates shed their winter fur before summer, but that of domesticated sheep grows continuously. Farmers shear the wool in early summer to produce a fleece, and to make their flocks comfortable in hot weather; the wool regrows during the autumn. Sheep have been bred to thrive under many different conditions from cool lush pasture to hot desert scrub.

Artificial selection has produced more than 60 breeds differing in body size, number of lambs per litter, horn conformation, colour and texture of wool. Mature rams of the largest breeds weigh more than 150 kg, three times the size of their mouflon ancestors, others grow very long, very thick or very fine wool, and/or enormous curled horns. Jacob’s sheep have four, sometimes six, horns and piebald fleeces.

Such changes are often, but not always, rapidly reversed in the ‘feral’ descendants of domesticated livestock that live wild without human supervision. The ancestors of Soay sheep were brought to the St Kilda islands, northwest Scotland by Neolithic farmers 3-4 Kya. Since people abandoned St Kilda a century ago, the sheep they left behind have become feral: like the ancestral mouflon, they are very small with relatively long legs, skittish temperament, dark brown hair as well as underfur that does not need shearing, and rarely give birth to more than a single lamb.

Cattle were domesticated from now the extinct aurochs (wild ox) as sources of meat & milk, hides & horn, this example has been carved and polished, and for use as draft animals, at about the same time and location as sheep, and later in India, becoming zebu cattle. In both cases, cattle were selectively bred for docility, smaller body size, the size and shape of the horns and capacity to cope with different diets. The horns have been removed from one of these skulls, but the other was hornless, with just rough growth zones where they would have grown. Endocrine control of letting down milk proved difficult to alter: for many centuries, cows would release their milk only while their own calf was at their side, and even now, the presence of strangers, loud noise etc. can hinder the response. Most modern breeds of cattle are selected and managed for the quality and quantity of either meat or milk (and yoghurt, cheese and butter made from it), with hides to be made into leather a by-product of both (see Oak lower Shelves).

Pigs were domesticated from wild boar (see Box A1) also at about the same time and location as sheep, and separately in China several centuries later. Although still able to hybridize with their wild ancestors, most modern breeds pigs are twice the size as adults, produce up to four times as many piglets/litter, grow much faster reaching sexual maturity at half the age, have much longer backs, smaller tusks and minimal hair. Such rapid anatomical change leads to dental malformations in the breeding stock of many domesticated mammals, especially pigs, but most are harvested young, before such problems impair growth. A few small, slow-growing breeds have dense body hair, and can live outside year-round in climates similar to those of their wild ancestors.

Humans hunted wild equids long before horses and asses (=donkeys) (see Boxes A3 and B4) were domesticated 4000-5000 y ago in Central Asia and Eastern Europe, for their milk, meat and skins as well as for transport. Truly wild horses and asses are now almost extinct, though many feral populations do well over much of their previous natural range (e.g. descendants of the horses brought to North America by Spanish troops in C16th and C17th), and in Australia, where they have never occurred naturally.

Both two-humped Bactrian camels of central Asia (see Box B2), and one-humped dromedaries of north & east Africa and Arabia are also nomadic, and were domesticated several millennia ago. Like horses, they were kept for their rich milk, thick hair (see Oak lower Shelves) and tough skins as well as for transport. Camels brought to Australia from northwest India and Afghanistan in the C19th for transport have produced large feral populations in much of north & central Australia, but now only a few truly wild camels remain in northwest China and Mongolia.

After the deaths (whether natural or induced) of all domesticated livestock, the meat, horn, feathers, hair and skin (see Oak lower Shelves), and perhaps certain tendons, bones and teeth, are harvested, then further useful materials from the rest of carcass are extracted by heating. The lipids in the adipose tissue, brain and bones melt and drain off to form tallow, of which the fatty acid compositions, and hence melting temperatures and oxidation in air, are slightly different in each species, reflecting their diets and digestive mechanisms. The various types of tallow are used in cookery, for making soap, lubricants and biofuel, and previously for candles, lotions, waterproofing for leather and cloth. The remains are boiled to produce soup stock and gelatin, then ground for animal feed supplements, fertilizers and as an ingredient of ‘bone china’. Most of these products are, at least slowly, biodegradable.

Genetic studies show that dog domestication from timber wolves (see Box B2) started at least 20, perhaps 40 Kya, though exactly when, where, why and how are still being investigated. As outlined for Box B1, human range, diet and technology were expanding rapidly during the Upper Palaeolithic.

Timber wolves are territorial, hunting and breeding in family packs, instincts that motivate adult dogs to adopt human groups and their homes as their own territory, which they thus defended from intruders. Dogs deploy growls, whines and howls plus facial expressions and postures of the body and tail to communicate with people as their ancestors did with each other. When lost or frightened, wolf pups attract attention with a little bark. Dogs bark more loudly and more readily, and retain the capacity to do so throughout life, probably due to selective breeding. Dogs have much better hearing and olfaction than people, enabling them to respond promptly to the smell, sound or sight of danger by barking to summon help from their human ‘families’, and to respond to their commands.

Selective breeding for specific human uses has produced dogs with differences in anatomy, temperament, habits, and often coincidentally, metabolic peculiarities. People living around the eastern Mediterranean and Mesopotamia during the first and second millennium BC developed dogs for hunting wild animals, guarding property and herding livestock.

Greyhounds were bred to gallop far and fast, hence the long slender legs, flexible lower back and thin smooth hair, and to hunt by sight in open country, hence the distinctive head-up posture maintained even while running. Bloodhounds were developed c. 1000 CE, and the later foxhounds hunted in European forests and farmland; they find and follow ‘prey’ by scent, running with the head down and nose close to ground. Mastiffs are big, muscular dogs with powerful jaws and fierce temperaments, first bred in ancient Assyria where they were deployed as guards, in battle and for gladiatorial displays.

As farming domesticated livestock spread west into Europe, several differing kinds of herding dogs emerged, developing the capacity for sophisticated communication with their shepherds. Most other modern dog breeds have been created since the C18th, many retaining juvenile traits such as floppy ears, short snouts and fluffy fur into adulthood. Most dog breeds, massive (weighing up to 100 kg) and miniature (1-2 kg), can still interbreed with each other and with wolves (apart from the mechanical incompatibilities involved), thus domestication has created one of the most anatomically diverse species on Earth.

Cats (see also Box B2) were more recently domesticated from the African wild cat Felis lybica. In Ancient Egypt, cats replaced snakes as the means of controlling the vermin that infested human food stores, and were later venerated as deities. Pest control continued as cats’ main role throughout North Africa & Europe and later in Asia, where strains such as Siamese with blue eyes and pale fur and Persians with long, fine haired were selectively bred as glamorous ornaments and companions.

Mature males fight with each other, especially while nearby females are sexually receptive, and usually stay near their human-provided homes, but they do not guard them. Although the populations of almost all wild felids are in decline, with tigers, cheetahs, lynx and several other species critically endangered, domestic cats are now major predators on wildlife almost worldwide, especially where they have established feral populations, as in Australia.

At about the same time, ferrets were domesticated from European polecats, mustelids similar to mink (see Box A2), primarily for catching fossorial prey such as rabbits and rats. Much later they were tamed as amusing pets.

However, the majority of mammals have proved unsuitable for domestication, usually because of their innate social behaviour. Deer were hunted for millennia before pastoralism (see Box A1), and their meat, antlers and skins are still much valued (see Boxes A3 & B2) but, except for reindeer (see Oak 2nd Shelf), they are territorial. Dominant males defend specific patches of land where their females and offspring forage, adult males become aggressive, families resist being herded together into large groups, are not easily led by people. In large parks and moorland, fallow deer and red deer live much as their ancestors did until harvested by the people who have protected them from their natural predators, but they are not selectively bred. A few mammals, notably Asian elephants (see Box C3), have long been tamed but cannot be domesticated. Young female elephants are caught from wild herds and trained to serve human needs, but they are rarely bred in captivity, mainly due to the enormous cost of maintaining bulls that become dangerous when in ‘musth’.

Birds have been food, service and companion animals since ancient times: large raptors (see Box D2) were bred and trained to catch small mammals and other prey for humans, homing pigeons (see Box C4) to carry messages, they and quail, peafowl, flamingos and various passerines were kept as ornaments.

Birds that are mainly herbivorous (see Boxes C4 and D3) produce better tasting meat and eggs and are easier to manage in captivity, as with mammals. Ducks, geese, pigeons and more recently turkeys, ostriches and quails, have long been farmed for eggs & meat and for plumage, such as goose down, that is still much valued for bedding and winter clothing. But by far the most abundant are domesticated forms of junglefowl (see Box D3), omnivorous, ground-nesting birds that roam the forests of India and SE Asia as flocks dominated by an elaborately feathered adult male. Selective breeding of ‘chickens’ during the past 8000 y has produced numerous varieties of different size and colour and most important of all, hens that lay eggs throughout the year and without the presence of a cock. Strains bred since the 1950s for their meat grow so fast that they can be harvested at 6-8 weeks old, but bodies become too heavy for the relatively small legs. Laying hens are past their best after 1.5-2 y and longevity, even under ideal conditions, of all modern chickens is much reduced compared to their wild ancestors. In C21st, domesticated chickens are by far the most numerous of all birds living on Earth.

Wild caught specimens of several species of the crow, starling (especially mynah birds), finch and parrot families have for millennia been renowned as companions for their capacity to imitate human speech and other artificial sounds. All such birds live naturally in flocks, form strong lasting pair bonds and have a varied diet. That many have been little studied in the wild became apparent after implementation of the CITES legislation in 1975 intensified efforts to breed large parrots in captivity. Far more is known about the behaviour of African grey parrots (see Boxes C4 and D3) in captivity than in the wild.

A few insects have also been domesticated for materials and food: wax for candles, polishes and lubricants as well as honey from honeybees, and silk, which is strands of secreted protein collected from the cocoons of ‘silkworms’. The wild moth Bombyx mandarina, whose caterpillars feed only on the leaves of a few closely related species of mulberry trees (see comments on Box D3), has been selectively bred for the past 5,000 y becoming a separate species, B. mori. This highly domesticated insect can complete its lifecycle only under artificial conditions. It is bigger than its wild ancestor, the adults are flightless and need help to mate, the caterpillars eat only one species of mulberry, but they are larger, tolerate living at very high density and a single long white thread can be unwound from their cocoons. These threads are processed into fabrics that are warm, comfortable, hard-wearing, washable and can easily be dyed. A kilogram of silk cloth requires 3-7K silkworms.

This Box displays a few animals of many different taxa that have been intentionally or accidently introduced to areas where they did not occur naturally, and the consequences for some of the local indigenous species. The long-term outcomes of such invasions are poorly understood and so very unpredictable, but obvious factors, such as climate and availability of the same foods in the homeland as in the new colony seem to have minimal impact, especially for terrestrial vertebrates.

The Great Lakes situated between USA and Canada had thriving populations of many different species of teleost fish and the silver lamprey (lower specimen) that had long been harvested by both native people and immigrants. Lampreys are jawless agnathans, descendants of the earliest group of fish that first appeared in the late Cambrian. An external parasite that attaches itself to other fish and eats its skin and scales, it grows to about 0.3 m long and rarely kills its host. The apparently similar sea lamprey (upper specimen) is found in coastal waters around both sides of the North Atlantic. Adults, which grow up to 3 m long, migrate into rivers to spawn then die. The larvae spend several years in freshwater eating small invertebrates and detritus, before moving to the sea where they become ectoparasites on many species of marine fish, but are not overabundant and do not obviously damage populations of other fish. The Welland canal built in the 1820s and the St. Lawrence Seaway completed in 1959 to bring large ships to Chicago, Duluth and Canadian ports also enabled sea lampreys to swim from the Atlantic Ocean into all the Great Lakes. The invaders had not coevolved with their hosts, and they decimate its populations of the indigenous fish including that of the silver lamprey.

Many other accidentally introduced fish, notably Nile perch to Lake Victoria in the 1970s and lionfish to the Western Atlantic and Caribbean region, have drastically altered long-established ecosystems.

Although many amphibians and reptiles are in decline, a few species have become invaders. This red-eared pond turtle was found alive in a ditch around Christ Church meadow in 2012. It was probably a discarded pet acquired during the Ninja turtle craze of the 1990s that had grown large on the waste from visitors’ picnics. In 2016, restrictions on keeping this species were introduced after it was found to be breeding in British canals, ponds and slow-flowing rivers, including backwaters of the Thames. African clawed frogs (see also Box D4) were, from the late 1940s, bred for biological research and for use in medical diagnosis, and later the pet trade. Some escaped and established feral populations in Britain, France, Japan, Chile and California; they turned out to be asymptomatic carriers of a highly infectious chytrid fungus that is lethal to many other frogs and toads, leading to the probable extinction of some species.

Burmese pythons, similar to the African python in Box D4, were popular pets, at least as juveniles, but released specimens established flourishing populations, first in the swampy Everglade region of Florida, now in most of the State. Predatory mammals and birds take eggs and hatchlings, and alligators eat a few, but the snakes have decimated populations of indigenous species including opossums, raccoons, bobcats and marsh rabbits. Well-equipped and well-funded efforts to cull them have had little impact. Paradoxically, the pythons are becoming rare over much of their natural range in Southeast Asia, where local people have long valued them for their meat and skins.

The surface to volume ratio is higher in small mammals, so they usually have denser underfur than larger animals, for whom heat dissipation as well as insulation is important (see Boxes B3, C2, D2 and Oak lower Shelves). Mink are semi-aquatic mustelids (see also Box A2) native to both Europe and North America, especially cold regions, but the American species is larger and more adaptable, living in a greater range of habitat. Both species were hunted and trapped for their soft, smooth water-repellent fur, but demand exceeded supply. Captive breeding began in the late C19th, first in USA and from the 1920s in Europe, where escapees have flourished, preying on the local fauna, and driving some, including water voles and the European mink to near extinction.

Other small mustelids have also become serious pests. European stoats were released in New Zealand before 1900 to control the rabbits introduced there during the previous century. But they, plus introduced rats, cats and Australian possums, found easier prey in local flightless birds, including kiwi and kakapo, the eggs & chicks of other native ground-nesting birds and the endemic tuatara, the last extant species of Rhynchocephalia, a previously diverse order of reptiles that has survived since the Triassic. A century of trapping and poisoning has only slowly improved protection these indigenous species. Feral ferrets are being eradicated from British islands where ground-nesting seabirds breed, including Guernsey, Shetland, Harris and Rathlin.

The career of the South American coypu (see Box D3) was similar to that of mink: captive bred for its dense, water-repellent fur in Britain and elsewhere in Europe from the late 1920s, soon escaped and established feral populations. By the 1960s, there were more 200,000 feral coypu in Britain, grazing crops and damaging the banks of rivers and canals. Fortunately most preferred the low-lying agricultural land in southern and eastern England, which thus became of focus of an eradicate campaign costing millions of pounds and took more than 30 y to exterminate the species from Britain. Similar success was achieved in some parts of Europe, but feral coypu persist in the Netherlands, Germany and Ireland. Efforts to exterminate mink have been less successful except on small islands, and are ongoing. The coypu and mink skeletons in this Collection are among their by-products.

The grey squirrel from eastern USA was deliberated released as an ornament for parks and gardens in the British Isles during the late C19th and early C20th, and into mainland Europe after World War II. Bigger, bolder, an asymptomatic carrier of squirrelpox virus and better able to eat unripe nuts than the indigenous red squirrel, it has rapidly displaced the native species except in mountainous areas where predatory pine martens are still plentiful, and on some offshore islands.

Most bizarre and capricious of all is the introduction of one the largest and most dangerous of all African mammals to South America. Around 1980, a wealthy drug smuggler illegally imported four hippopotamuses for his private menagerie in the mountains of central Colombia. After he died in 1993, most of the smaller, more manageable animals were relocated to zoos, but the hippos were abandoned. They escaped into the lush equatorial valley of the Magdalena River nearby where the population grew to around 200 within 30 y. Scores of hippos have been caught and transferred to overseas zoos at great expense, but many others remain, damaging indigenous flora and fauna. With no local predators strong enough to tackle them, without further intervention, there could be over 1,000 by 2035.

Many introduced birds, mynahs, other starlings and some crows and parrots have become invasive species. A local example is the ring-necked parakeet, which is native to northern India but was accidentally introduced about 50 y ago, and has proliferated rapidly; 30,000 are said to live in Greater London, with more throughout SE England, including Oxford. Budgerigars, small parrot relatives native to central Australia, have become Britain’s favourite avian pet, and since the 1840s have been bred in captivity, often outdoors; some must have escaped, but they have not established feral populations like ring-necked parakeets.

This species of giant African land snail is native to tropical west Africa (other closely related species from elsewhere in Africa share its habits and common name) where it eats a wide variety of herbaceous plants, breeds prolifically and is protected by its thick, hard shell. These qualities have enabled them to become important agricultural pests in tropical and subtropical areas of SE Asia, Polynesia, Caribbean Islands and the Americas after a few young specimens were accidently introduced during the C20th. As well as destroying crops and gardens, they spread plant and human diseases. Most indigenous predators can kill only very young specimens. Efforts to eradicate them have been successful only in dry climates such as Australia.

White-clawed crayfish are Britain’s only indigenous decapod crustacean. These omnivores were widespread and often common in lakes, canals and rivers, especially chalk streams, where, as well as sustaining fish, herons, otters and other riverine predators, for millennia people harvested them as a much-valued food. The species is now critically endangered following the accidental escape of exotic crayfish bred in local commercial farms for even larger meals. The North American signal crayfish (Pacifastacus leniusculus) invaded in the 1970s. Adults are larger and more aggressive than the indigenous species and they transmit crayfish plague, an infectious oomycete fungus, to which the natives no resistance. In the 1990s, the red swamp crayfish Procambarus clarkii, also from North America, escaped from cultivation and soon bred in the wild. It digs deep burrows that damage riverbanks – it is a serious pest in the River Thames – and pollute the water. Introductions of these invasive species elsewhere in Europe and in Southeast Asia have caused drastic declines to populations of indigenous crayfish species and to other freshwater organisms. There was no sign of either invader in 1972-4 when these formalin-preserved specimens were collected from Oxfordshire rivers, though soon afterwards, the indigenous species disappeared.